1. Field of the Invention
The present invention relates to a method for manufacturing a camshaft of the type having a solid or tubular shaft of steel and a plurality of fitting members, such as cam lobes, journals and gears which are separately fabricated from metal powders and fitted on the shaft by a liquid-phase sintering process.
2. Description of the Prior Art
The composite camshaft as manufactured by the method disclosed under JP, B2, 58-13603 is provided with a steel shaft and a plurality of fitting members, such as cam lobes and journals, which are firmly bonded to the steel shaft by a liquid-sintering process. The fitting member is fabricated as a green compact from metal powders to have a bore for fitting engagement with the steel shaft and then sintered to yield a liquid phase and shrink, thereby being superior in wear resistance as well as bonding strength. When the green compact is sintered to shrink, it has a point in the bore which first adheres to the steel shaft to define a neutral cross-section of shrinkage in which there is no change in axial position and to which other cross-sections axially shift. The first adhering point or neutral cross-section is unexpectedly variable under treatment conditions. This gives the known camshafts a disadvantage in that the axial position or distance from the reference plane of each fitting member is not always held within a desired tolerance.